Method of forming thin film and method of modifying surface of thin film

ABSTRACT

A method including: a plasma contact step including supplying treatment gas including a reactant gas into a chamber, activating a reactant component included in the treatment gas by generating plasma from the reactant component by applying high-frequency power, and bringing the treatment gas including the reactant component activated into contact with the surface of the substrate, in which in the plasma contact step, a first plasma generation condition in which stable plasma is generated by applying high-frequency power of a first power level while supplying treatment gas of a first concentration is changed to a second plasma generation condition in which a desired thin film is obtained by performing at least one of increasing the high-frequency power to a second power level and gradually decreasing the treatment gas to a second concentration, and of gradually increasing the high-frequency power to the second power level, and abnormal electrical discharge is suppressed.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates generally to a method of forming a thin film by a plasma-enhanced atomic layer deposition (PEALD) process, and a method of modifying a surface of a thin film by using gas that is subjected to plasma generation.

Related Art

In a manufacturing step of a semiconductor device, a treatment such as a film forming treatment is performed with respect to a substrate such as a semiconductor wafer. Examples of a film forming method include a plasma-enhanced atomic layer deposition (PEALD) process, and in film-formation according to the PEALD process, a cycle is repeated in which a raw material gas component is adsorbed onto a substrate of a film-forming target in a chamber while the substrate is heated, and the chamber is purged, and then, a reactant gas or a carrier gas is supplied, the reactant gas or the carrier gas is subjected to plasma generation, a reactant component that is activated reacts with the raw material gas component that is adsorbed on the substrate, and thus, atomic layers are deposited one by one, and as necessary, a surface modification treatment is performed by using the gas subjected to the plasma generation, and therefore, a desired thin film is formed on the substrate.

As such a film forming method, for example, a method of depositing a silicon oxide film on a substrate, including one or a plurality of deposition cycles including a step of supplying a plurality of pulses of silicon raw material gas including N,N,N′,N′-tetraethyl diaminosilane to a reactor, and a step of supplying oxygen-containing gas onto the substrate in the reactor has been disclosed (refer to Patent Document 1).

Patent Document 1: U.S. Published Patent Application Publication, No. 2009/041952, Specification

SUMMARY OF THE INVENTION

In an atomic layer deposition (ALD) process, a power level of high-frequency power (RF power) that is applied at the time of generating plasma, a supply condition of a carrier gas or a reactant gas that is supplied into a chamber as a treatment gas, and the like are important parameters that affect film quality of a thin film to be obtained. In particular, it is possible to increase the quality of the thin film to be obtained by increasing the power level of the high-frequency power and optimizing the supply conditions of the reactant gas. But in the case of applying such high-frequency power at a high power level, plasma variation due to abnormal electrical discharge occurs resulting in a decrease in the quality of the film, and thus, it is difficult to obtain a desired thin film. In addition, in a process of modifying the surface of the thin film by using gas subjected to plasma generation, in a case where the abnormal electrical discharge occurs, it is difficult to obtain desired thin film. Therefore, it is desirable to generate stable plasma.

One aspect of the present disclosure is a method of forming a thin film on a surface of a substrate, the method including:

a plasma contact step including

supplying a treatment gas including a reactant gas into a chamber,

activating a reactant component included in the treatment gas by generating plasma from the reactant component by applying high-frequency power, and

bringing the treatment gas including the reactant component thus activated into contact with the surface of the substrate to form the thin film, in which in the plasma contact step, a first plasma generation condition is changed to a second plasma generation condition by adjusting at least one of concentration of the reactant component included in the treatment gas and power level of the high-frequency power, thereby suppressing abnormal electrical discharge.

According to the aspect of the present disclosure, it is possible to provide a method of forming a thin film in which, for example, even in a case where the reactant component included in the treatment gas is subjected to the plasma generation by applying plasma having a high power level, stable plasma can be generated by suppressing abnormal electrical discharge, and thus, a desired thin film can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical sectional view illustrating a film forming device as a substrate treatment device that is used in a method of forming a thin film;

FIG. 2 is a graph showing an example of a power level of high-frequency power (RF forward power (Fwd)) to be applied, an oxygen (O₂) concentration, and a self-bias voltage (Vdc), in a first embodiment;

FIG. 3 is a graph showing the power level of the high-frequency power (the RF forward power (Fwd)) to be applied, and the concentration of oxygen (O₂) that is a reactant component, in Examples 1 to 6 of the present invention, and is a graph at the time of changing a duration for maintaining the power level after a concentration of the reactant component reaches a second concentration (an RAMP time (1 second, 5 seconds, and 9 seconds)) and a first concentration (20% and 5%) of the reactant component;

FIG. 4 is a graph showing a variation in the power level of the high-frequency power (the RF forward power (Fwd)), the oxygen (O₂) concentration, and a flow rate of raw material gas, in each step of Examples 1 to 6 of the present invention;

FIG. 5 is a graph showing an example of the power level of the high-frequency power (the RF forward power (Fwd)) to be applied, the oxygen (O₂) concentration, and the self-bias voltage (Vdc), in a second embodiment;

FIG. 6 is a graph showing the power level of the high-frequency power (the RF forward power (Fwd)) to be applied, and the concentration of oxygen (O₂) as the reactant component, in Examples 7 to 12 of the present invention, and is a graph at the time of changing the duration for maintaining the power level after the concentration of the reactant component reaches the second concentration (the RAMP time (1second, 5 seconds, and 9 seconds)) and a first power level (0 W and 150 W);

FIG. 7 is a graph showing a variation in the power level of the high-frequency power (the RF forward power (Fwd)), the concentration of oxygen (O₂), and the flow rate of the raw material gas, in each step of Examples 7 to 12 of the present invention;

FIG. 8 is a graph at the time of changing the power level of the high-frequency power (the RF forward power (Fwd)) to be applied, the concentration of oxygen (O₂) that is the reactant component, the first concentration (5% and 10%) of the reactant component, and the first power level (50 W and 150 W), in Examples 13 to 16 of the present invention;

FIG. 9 is a graph showing a variation in the power level of the high-frequency power (the RF forward power (Fwd)), the oxygen (O₂) concentration, and the flow rate of the raw material gas, in each step of Comparative Example 1;

FIG. 10 is a graph showing a variation in the power level of the high-frequency power (the RF forward power (Fwd)), the oxygen (O₂) concentration, and the flow rate of the raw material gas, in each step of Example 17 of the present invention;

FIG. 11 is a graph showing a variation in the power level of the high-frequency power (the RF forward power (Fwd)), the oxygen (O₂) concentration, and the flow rate of the raw material gas, in each step of Example 18 of the present invention; and

FIG. 12 is a graph showing the power level of the high-frequency power (the RF forward power (Fwd)) to be applied, the oxygen (O₂) concentration, and the self-bias voltage (Vdc), in an aspect of the related art.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. Note that, the present invention is not limited to the following embodiments, but can be variously changed within a range not departing from the gist of the present invention.

<<Method of Forming Thin Film>>

A method of forming a thin film according to this embodiment is a method of forming a thin film, including: a plasma contact step of supplying treatment gas including reactant gas into a chamber, of activating a reactant component (a gas component that is activated by the plasma generation) included in the treatment gas by generating plasma from the reactant component by applying high-frequency power, and of bringing the treatment gas including the reactant component thus activated by the plasma generation into contact with the surface of the substrate to form the thin film, in which in the plasma contact step, a first plasma generation condition is changed to a second plasma generation condition by adjusting one or both of a concentration of the reactant component in the treatment gas and a power level of the high-frequency power, thereby suppressing abnormal electrical discharge.

In the method of forming a thin film according to this embodiment, first, stable plasma is generated in the first plasma generation condition or a condition close thereto, and thus, even in a case where the first plasma generation condition is changed to the second plasma generation condition by adjusting at least one of the concentration of the reactant component in the treatment gas and the power level of the high-frequency power, the generation of the stable plasma is maintained, and generation of plasma from the reactant component included in the treatment gas is accelerated by adjusting the concentration of the reactant component or the power level of the high-frequency power. For this reason, it is possible to provide a method of forming a thin film in which even in a case where the reactant component included in the treatment gas is subjected to the plasma generation by applying plasma having a high power level, abnormal electrical discharge due to parasitic plasma or the like can be suppressed, and stable plasma can be generated.

In the method of forming a thin film according to this embodiment, the thin film is prepared by a plasma-enhanced atomic layer deposition (PEALD) process including a supply step of supplying at least the raw material gas including a raw material component into the chamber and of adsorbing the raw material gas component on a surface of the substrate, a discharge step of discharging any of the raw material gas component that is not adsorbed on the substrate from the chamber. And the plasma contact step described above, and a PEALD process progresses on the basis of a surface reaction that is controlled, in general, self-controlled. Here, a reaction between the raw material gas and the reactant gas that are included in the treatment gas, in a gas phase, can be reduced by alternately performing the supply of the raw material gas with respect to the substrate and the contact of the reactant gas or carrier gas that is subjected to the plasma generation by the application of the high-frequency power with respect to the substrate. According to the PEALD process of this embodiment, it is possible to form a thin film having a high step coverage, and thus, it is possible to preferably form the thin film on a three-dimensional structure on the substrate.

Herein, a “thin film of high film quality” indicates a thin film having high film quality, and more specifically, indicates a thin film having a small wet etch rate ratio (WERR). Here, the WERR of the thin film is a ratio of mass decrease in an ALD film to a mass decrease in the TOX film at the time of simultaneously dipping the ALD film and a thermal oxide film thereof (the TOX film) in diluted hydrofluoric acid. And a numerical range at the time of forming a SiO₂ film as the ALD film is preferably less than 2.0, is more preferably less than or equal to 1.9, and is even more preferably less than or equal to 1.6.

In addition, herein, “stable plasma” indicates plasma that does not cause abnormal electrical discharge. The presence or absence of the abnormal electrical discharge at the time of applying the high-frequency power can be determined in accordance with a positive or negative value of a self-bias voltage (Vdc). Here, in a case where the abnormal electrical discharge occurs at the time of applying the high-frequency power, the self-bias voltage (Vdc) has a positive value. In addition, in a case where the abnormal electrical discharge does not occur even at the time of applying the high-frequency power, the self-bias voltage (Vdc) has 0 or a negative value.

<Film Forming Device>

A film forming device that is used in the method of forming a thin film according to this embodiment and a surface modification treatment method of a thin film is not particularly limited. But for example, a film forming device 1 as illustrated in FIG. 1 can be used.

FIG. 1 is a vertical sectional view schematically illustrating a film forming device as a substrate treatment device according to an embodiment of the present invention. In the film forming device 1 of FIG. 1, a thin film is formed on a substrate W such as a semiconductor wafer by a plasma-enhanced atomic layer deposition (PEALD) process.

The film forming device 1 includes an approximately cylindrical chamber 10 with a bottom of which the upper side is opened, and an installation stand 12 provided in the chamber 10, on which the substrate W is installed.

The chamber 10 is electrically grounded by a grounding wire that is not illustrated. In addition, an inner wall of the chamber 10, for example, is covered with a coated film (not illustrated) formed of a plasma resistant material on a surface.

The installation stand 12, for example, is formed of a metal material such as nickel. A lower surface of the installation stand 12 is supported by a support member 13 formed of a conductive material, and is electrically connected thereto. The support member 13 is electrically connected to a bottom surface of the chamber 10. For this reason, the installation stand 12 is grounded through the chamber 10, and functions as a lower electrode pairing with a gas supply unit 14 that functions as an upper electrode. A heater (not illustrated) is embedded in the installation stand 12, and thus, it is possible to heat the substrate W that is installed on the installation stand 12 to a predetermined temperature.

Here, the size of an air gap D between the installation stand 12 that functions as the lower electrode and the gas supply unit 14 that functions as the upper electrode may be in a range in which plasma can be generated between the installation stand 12 and the gas supply unit 14, and for example, can be in a range of greater than or equal to 7 mm and less than or equal to 15 mm.

A lower portion of the support member 13 extends to the lower side through an insertion hole 11 that is formed in the central portion of a bottom portion of the chamber 10. The support member 13 can be moved up and down by a hoisting and lowering mechanism that is not illustrated, and thus, the installation stand 12 is hoisted or lowered.

In addition, a plurality of support pins (not illustrated) are provided on the lower side of the installation stand 12 and the inner side of the chamber 10. And insertion holes (not illustrated) into which the support pins are inserted are formed on the installation stand 12. When the installation stand 12 is lowered, the substrate W can be received by upper end portions of the support pins that penetrate through the insertion holes of the installation stand 12. And the substrate W can be transferred from or to a transport arm (not illustrated) that enters from the outside the chamber 10.

The gas supply unit 14 is provided on the upper side of the installation stand 12 in parallel to face the installation stand 12. In other words, the gas supply unit 14 is disposed to face the substrate W that is installed on the installation stand 12. The gas supply unit 14 supplies treatment gas for performing a treatment with respect to the substrate W, and for example, is formed of a conductive metal such as nickel (Ni), and also functions as the upper electrode.

An outer circumferential portion of an upper surface of the gas supply unit 14 is retained by an annular support member 16. The support member 16, for example, is formed of an insulating material such as quartz. The gas supply unit 14 and the chamber 10 are electrically insulated. Note that, a heater (not illustrated) may be provided on the upper surface of the gas supply unit 14.

A supply source (not illustrated) of the raw material gas or the reactant gas and the carrier gas that are the treatment gas is connected to the gas supply unit 14 through an external gas supply pipe of the film forming device 1. The raw material gas or the reactant gas, and the carrier gas that are supplied to the gas supply unit 14 are introduced to the chamber 10 through the gas supply hole 15 in the shape of a shower. Further, a gas supply condition adjustment unit including a valve, a mass flow controller, and the like is provided in the external gas supply pipe of the film forming device 1, and is capable of adjusting a gas supply condition of the treatment gas, such as a gas type, a gas mixing ratio, and a flow rate.

In addition, the gas supply unit 14 functions as the upper electrode. A high-frequency power source that supplies high-frequency power and generates plasma is electrically connected to the gas supply unit 14 through a matching box (not illustrated). The high-frequency power source, for example, is configured such that high-frequency power having a frequency of 100 kHz to 100 MHz can be output. The matching box matches internal impedance to load impedance of the high-frequency power source, and when plasma is generated in the chamber 10, it seems that the internal impedance and the load impedance of the high-frequency power source are identical to each other.

In addition, an exhaust mechanism that exhausts the inside of the chamber 10 is connected to a side surface of the chamber 10. The environment in the chamber 10 can be exhausted by driving the exhaust mechanism, and the pressure can be reduced to a predetermined vacuum degree.

First Embodiment of Method of Forming Thin Film

In a first embodiment of the method of forming a thin film according to this embodiment, a thin film is prepared on the substrate by the plasma-enhanced atomic layer deposition (PEALD) process. And when the reactant component (the gas component that is activated by the plasma generation) of the treatment gas is subjected to the plasma generation by applying the high-frequency power into the chamber, the first plasma generation condition in which high-frequency power of a second power level that is identical to that of the second plasma generation condition described below is applied while the treatment gas in which the concentration of the reactant component is the first concentration is supplied is changed to the second plasma generation condition by gradually decreasing the concentration of the reactant component to a second concentration from the first concentration while applying the high-frequency power of the second power level.

[Substrate and Preparation Thereof]

In forming a thin film, first, the substrate W is taken into the chamber 10, and is installed and retained on the installation stand 12. A silicon substrate, a germanium substrate, and the like can be used as the substrate W. But the substrate W is not limited thereto. In addition, the substrate W is taken into the chamber 10 in a vacuum state by using a load lock chamber or the like that is not illustrated.

The substrate W that is installed on the installation stand 12 is heated by using a heater. Here, a heating temperature of the substrate W, for example, can be in a range of 50° C. to 500° C. At this time, the carrier gas is supplied into the chamber 10. Here, for example, at least one selected from the group consisting of helium (He) gas, argon (Ar) gas, and hydrogen (H₂) gas can be used as the carrier gas. At this time, an internal pressure of the chamber 10, for example, can be in a range of greater than or equal to 50 Pa, and can be preferably in a range of greater than or equal to 300 Pa. And an upper limit thereof can be in a range of less than or equal to 1300 Pa, and can be preferably in a range of less than or equal to 1000 Pa. Note that, the reactant gas described below may be supplied along with the carrier gas.

[Raw Material Gas Supply Step]

Next, at least the raw material gas is supplied into the chamber 10. At this time, the carrier gas or the reactant gas may be supplied to the chamber 10 along with the raw material gas. Accordingly, the raw material gas is adsorbed onto the substrate W, and thus, a molecular layer of the raw material gas is formed on the surface of the substrate W. Here, examples of the raw material gas including materials that can be used in the plasma-enhanced atomic layer deposition (PEALD) process, it is preferable to use aminosilane, and more specifically, it is possible to use at least one selected from the group consisting of bis(diethyl amino)silane (BDEAS), diisopropyl aminosilane (DIPAS), tetrakis(dimethyl amino)silane (4DMAS), tris(dimethyl amino)silane (3DMAS), bis(dimethyl amino)silane (2DMAS), tetrakis(ethyl methyl amino)silane (4EMAS), tris(ethyl methyl amino)silane (3EMAS), bis(tart-butyl amino)silane (BTBAS), and bis(ethyl methyl amino)silane (BEMAS). In addition, a flow rate of the raw material gas to be supplied into the chamber 10 can be approximately in a range of greater than or equal to 25 sccm. And can be preferably in a range of greater than or equal to 50 sccm, and an upper limit thereof can be approximately in a range of less than or equal to 3000 sccm, and can be preferably in a range of less than or equal to 2000 sccm. In addition, a supply time of the raw material gas, for example, can be in a range of longer than or equal to 0.05 seconds, and can be preferably in a range of longer than or equal to 0.2 seconds. And an upper limit thereof can be in a range of shorter than or equal to 5.0 seconds, and can be preferably in a range of shorter than or equal to 0.5 seconds. An optimal supply time of the raw material gas can be set on the basis of a condition such as the type of raw material gas and the internal pressure of the chamber.

[Purge Step]

An excessive raw material gas component that is not adsorbed on the substrate W is discharged from the chamber after the raw material gas is supplied (a purge step or discharge step). Accordingly, the contamination of the thin film due to the raw material gas remaining in the environment is reduced, and thus, it is possible to obtain a flatter thin film. Here, examples of a section of discharging the raw material gas component that is not adsorbed on the substrate W from the chamber include a section of purging the raw material gas component that is not adsorbed on the substrate W by supplying the reactant gas, the carrier gas, or mixed gas of the reactant gas and the carrier gas into the chamber 10, a section of discharging the raw material gas component by vacuuming the chamber 10, and a combination thereof. Among them, in particular, it is preferable that the raw material gas component is purged by supplying gas including the reactant gas into the chamber 10, and it is more preferable that the raw material gas component is purged by supplying the treatment gas described below. As described above, the raw material gas component that is not adsorbed on the substrate W is discharged from the chamber 10, and thus, the contamination of the thin film due to the raw material gas remaining in the environment of the chamber 10 is reduced, and therefore, it is possible to obtain a flatter thin film. In particular, the raw material gas component is purged at a ratio at the time of starting the application of the high-frequency power, and thus, it is possible to smoothly perform the generation of plasma described below and the formation of a thin film.

[Plasma Contact Step]

Next, the treatment gas including the reactant gas is supplied into the chamber 10, and the high-frequency power is applied to the gas supply unit 14, and thus, the reactant component (the gas component that is activated by the plasma generation) of the treatment gas is subjected to the plasma generation. Then, the reactant component that is activated by the plasma generation, included in the treatment gas reacts with the raw material gas component that is adsorbed on the substrate W by bringing the treatment gas including the reactant component that is activated by the plasma generation into contact with the surface of the substrate W, and thus, even in a case where the surface of the substrate W has a three-dimensional structure, it is possible to form a thin film having a uniform thickness on the surface.

For example, in a case where the reactant gas and the carrier gas are supplied into the chamber 10, as the treatment gas, the reactant component consisting of at least one of the reactant gas and the carrier gas is subjected to the plasma generation by applying the high-frequency power, and the reactant component reacts with the raw material gas component by bringing the reactant component that is activated by the plasma generation into contact with the raw material gas component that is adsorbed on the substrate W, and thus, it is possible to form a thin film having a uniform thickness on the surface of the substrate W.

In this embodiment, when plasma is generated by applying the high-frequency power, stable plasma is generated in the first plasma generation condition in which the high-frequency power of the second power level that is identical to that of the second plasma generation condition is applied while the treatment gas in which the concentration of the reactant component is the first concentration is supplied, and then, the first plasma generation condition is changed to the second plasma generation condition in which a thin film of high film quality is formed by gradually decreasing the concentration of the reactant component included in the treatment gas that is supplied to the chamber 10 to the second concentration from the first concentration while applying the high-frequency power of the second power level.

In the second plasma generation condition in which a thin film of high film quality is formed, even in the case of generating plasma by applying the high-frequency power to the treatment gas in which the concentration of the reactant component is low, as it is obvious from the fact that the self-bias voltage (Vdc) has a positive value, the abnormal electrical discharge easily occurs, and there are many cases where it is difficult to generate stable plasma (FIG. 12). From such a viewpoint, in the method of forming a thin film of this embodiment, in the first plasma generation condition, stable plasma is generated by applying the high-frequency power (RF forward power (Fwd)) to the treatment gas in which the concentration of the reactant component is relatively high, and then, the first plasma generation condition is changed to the second plasma generation condition in which a thin film of high film quality is formed by gradually decreasing the concentration of the reactant component (for example, a concentration of oxygen (O₂) gas) to the second concentration, and thus, in the second plasma generation condition, the generation of stable plasma is also maintained. For this reason, the self-bias voltage (Vdc) has a negative value, and thus, it is possible to generate stable plasma without any abnormal electrical discharge (FIG. 2).

Gas that is capable of reacting with the raw material gas described above in the presence of the gas component that is subjected to the plasma generation can be used as the reactant gas included in the treatment gas. More specifically, it is preferable to use at least one selected from the group consisting of oxygen (O₂) gas, nitrous oxide (N₂O) gas, carbon dioxide (CO₂) gas, nitrogen (N₂) gas, and ammonia (NH₃) gas. In addition, as described above, it is preferable to use at least one selected from the group consisting of helium (He) gas, argon (Ar) gas, and hydrogen (H₂) gas, as the carrier gas.

The first concentration of the reactant component included in the treatment gas, for example, can be in a range of greater than or equal to 3 volume %, and can be preferably in a range of greater than or equal to 5 volume %. And an upper limit thereof can be in a range of less than or equal to 50 volume %, and can be preferably in a range of less than or equal to 20 volume %. In addition, the second power level of the high-frequency power (the RF forward power (Fwd)), for example, can be in a range of greater than or equal to 100 W, and can be preferably in a range of greater than or equal to 200 W. And an upper limit thereof can be in a range of less than or equal to 1000 W, and can be preferably in a range of less than or equal to 500 W. In particular, the first concentration is set to be greater than or equal to 20 volume %, and thus, even in the case of applying high-frequency power of greater than or equal to 100 W at which a thin film of high film quality can be formed, it is difficult to cause the abnormal electrical discharge, and therefore, it is possible to generate stable plasma in a state of applying the high-frequency power. On the other hand, the first concentration is set to be less than or equal to 20 volume %, and thus, when the concentration of the reactant component is decreased to the second concentration, it is possible to reduce fluctuations in the concentration of the reactant component, and therefore, it is possible to increase the productivity of the film forming device 1.

In addition, the second concentration of the reactant component included in the treatment gas is a value that is lower than the first concentration, and for example, can be in a range of greater than or equal to 1 volume %. And can be preferably in a range of greater than or equal to 2 volume %, and an upper limit thereof can be in a range of less than or equal to 10 volume %, and can be preferably in a range of less than or equal to 5 volume %. The concentration range is a range in which a thin film of high film quality can be formed, but is also a concentration range in which it is difficult to generate stable plasma, in particular, at the time of applying the high-frequency power of the second power level. In the method according to this embodiment, even in a case where the concentration of the reactant component included in the treatment gas to be supplied to the chamber 10 is decreased to the second concentration from the first concentration, stable plasma is continuously generated, and thus, it is difficult to cause the abnormal electrical discharge, and it is possible to form a thin film of high film quality.

In addition, when the concentration of the reactant component included in the treatment gas is decreased to the second concentration from the first concentration, a rate of change of the concentration of the reactant component as a function of time, for example, can be in a range of greater than or equal to 0.3 volume %/second, and can be preferably in a range of greater than or equal to 0.5 volume %/second. And an upper limit thereof can be in a range of less than or equal to 100 volume %/second, and can be preferably in a range of less than or equal to 80 volume %/second. In particular, the rate of change of the concentration is set to be greater than or equal to 1 volume %/second, and thus, it is possible to make the occurrence of the abnormal electrical discharge due to the application of the high-frequency power difficult.

A duration to apply the high-frequency power after the concentration of the reactant component reaches the second concentration, for example, can be in a range of longer than or equal to 0.05 seconds, and can be preferably in a range of longer than or equal to 0.2 seconds. And an upper limit thereof can be in a range or shorter than or equal to 600 seconds, and can be preferably in a range or shorter than or equal to 20 seconds.

Examples of a section of adjusting the concentration of the reactant component include changing a supply ratio of the reactant component that is subjected to the plasma generation, and a non-reactant component that is not subjected to the plasma generation. For example, in a case where the reactant component consists of the reactant gas, changing a supply ratio of the reactant gas and the carrier gas with respect to the chamber 10 is exemplified. At this time, a supply amount of the reactant gas with respect to the chamber 10 may be decreased, or a supply amount of the carrier gas may be increased.

A flow rate of the treatment gas that is supplied to the chamber 10 at the time of forming a thin film is not particularly limited, but can be approximately in a range of greater than or equal to 1500 sccm, and can be preferably in a range of greater than or equal to 2500 sccm. And an upper limit thereof can be in a range of less than or equal to 7500 sccm, and can be preferably in a range of less than or equal to 5000 sccm.

The internal pressure of the chamber 10 at the time of forming a thin film may be a size in a range that can be applied to the plasma-enhanced atomic layer deposition (PEALD) process, but is not particularly limited, and for example, can be in a range of greater than or equal to 100 Pa, and can be preferably in a range of greater than or equal to 200 Pa. And an upper limit thereof can be in a range of less than or equal to 1000 Pa, and can be preferably in a range of less than or equal to 800 Pa.

The reactant component included in the treatment gas is activated by the plasma generation of the reactant component included in the treatment gas, and for example, radicals of the reactant gas or the carrier gas, atoms of the reactant gas or the carrier gas, and plasma of the reactant gas or the carrier gas are generated. Then, the reactant gas that is activated by plasma generation, included in the treatment gas reacts with the raw material gas component that is adsorbed on the substrate, and thus, it is possible to form a single layer of a thin film.

[By-Product Discharge Step]

The single layer of the thin film is formed, and then, a by-product that is generated by a reaction between the reactant component and the raw material gas component is discharged from the chamber. Here, examples of a section of discharging the by-product from the chamber include a section of supplying at least one of the reactant gas and the carrier gas into the chamber 10 and of purging the raw material gas component that is not adsorbed on the substrate, a section of vacuuming the chamber 10 and of discharging the raw material gas component, and a combination thereof.

[Formation of Thin Film Having Desired Thickness]

The by-product is discharged from the chamber 10, and then, a cycle is repeated in which the raw material gas component is adsorbed on the substrate W, the excessive raw material gas component is discharged from the chamber 10, the treatment gas including the reactant gas is supplied into the chamber 10, the reactant component in the treatment gas is subjected to the plasma generation by applying the high-frequency power to the gas supply unit 14 and reacts with the raw material gas component to form a thin film. And the by-product is discharged from the chamber, and thus, it is possible to form a thin film having a desired thickness on the substrate W. Here, the thickness of the thin film is the thickness of a monomolecular layer, and can be in a range of greater than or equal to 0.0001 μm. And an upper limit thereof can be in a range of less than or equal to 1 μm, and can be preferably in a range of less than or equal to 0.1 μm.

Examples of the thin film that is obtained by this embodiment include a SiO₂ film, a SiN film, or a SiC film. Such a thin film that is useful in a semiconductor device is formed by the plasma-enhanced atomic layer deposition (PEALD) process, and thus, it is possible to obtain a semiconductor device with higher quality and high reliability.

Second Embodiment of Method of Forming Thin Film

In a second embodiment of the method of forming a thin film according to this embodiment, the thin film is prepared on the substrate by the plasma-enhanced atomic layer deposition (PEALD) process. And in the plasma contact step, when the reactant component in the treatment gas is subjected to the plasma generation by applying the high-frequency power into the chamber, the first plasma generation condition in which the high-frequency power of the first power level is applied or the high-frequency power is not applied while the treatment gas in which the concentration of the reactant component is the second concentration that is identical to that of the second plasma generation condition described below is supplied is changed to the second plasma generation condition by gradually increasing the power level of the high-frequency power to the second power level while supplying the treatment gas of the second concentration.

In the method of forming a thin film of this embodiment, the concentration of the reactant component included in the treatment gas (for example, oxygen (O₂) gas) in the first plasma generation condition is the second concentration at which a thin film of high film quality can be formed, and the first power level of the high-frequency power is lower than a power level at which a thin film of high film quality can be formed. Stable plasma is generated at a power level that is close to the first plasma generation condition and is relatively low by gradually increasing the power level of the high-frequency power (the RF forward power (Fwd)) from such a first plasma generation condition, and then, the power level is gradually increased to the first power level at which a thin film of high film quality can be formed, and thus, the generation of stable plasma is maintained. For this reason, the self-bias voltage (Vdc) has a negative value, and it is possible to generate stable plasma without any abnormal electrical discharge (FIG. 5).

Here, the first power level that is applied before the high-frequency power is gradually increased is not particularly limited, and for example, may be gradually increased from 0 W (a state in which the high-frequency power is not applied). On the other hand, from the viewpoint of reducing a time required for increasing the high-frequency power while making the occurrence of the abnormal electrical discharge difficult, the first power level, for example, can be in a range of greater than or equal to 50 W, and can be preferably in a range of greater than or equal to 100 W. An upper limit of the first power level can be in a range of less than or equal to 1000 W, and can be preferable in a range of less than or equal to 500 W. In particular, the first power level is set to be less than or equal to 1000 W, and thus, even in a case where the second concentration is high, it is difficult to cause the abnormal electrical discharge, and therefore, it is possible to generate stable plasma.

In addition, the second concentration of the reactant component included in the treatment gas, for example, can be in a range of greater than or equal to 1 volume %, and can be preferably in a range of greater than or equal to 2 volume %. And an upper limit thereof can be in a range of less than or equal to 20 volume %, and can be preferably in a range of less than or equal to 10 volume %.

On the other hand, the second power level after the high-frequency power is increased is a value higher than the first power level, and for example, can be in a range of greater than or equal to 100 W, and can be preferably in a range of greater than or equal to 200 W. And an upper limit thereof can be in a range of less than or equal to 1500 W, and can be preferably in a range of less than or equal to 1000 W. The range of the power level is a range in which a thin film of high film quality can be formed at a concentration range in which it is difficult to generate stable plasma, in particular, at the time of supplying the treatment gas in which the concentration of the reactant component is the second concentration into the chamber 10. In the method according to this embodiment, the power level of the high-frequency power to be applied is gradually increased to the second power level from the first power level, and thus, stable plasma is continuously generated, and therefore, it is difficult to cause the abnormal electrical discharge, and it is possible to form a thin film of high film quality.

In addition, a rate of change of the high-frequency power at the time of increasing the high-frequency power to the second power level, for example, can be in a range of greater than or equal to 5 W/second, and can be preferably in a range of greater than or equal to 8 W/second. And an upper limit thereof can be in a range of less than or equal to 5000 W/second, and can be preferably in a range of less than or equal to 3000 W/second. In particular, the rate of change of the high-frequency power is set to be less than or equal to 10 W/second, and thus, it is possible to make the occurrence of the abnormal electrical discharge due to the application of the high-frequency power difficult.

A duration to apply the high-frequency power after the power level of the high-frequency power reaches the second power level, for example, can be in a range of longer than or equal to 0.05 seconds, and can be preferably in a range of longer than or equal to 0.2 seconds. And an upper limit thereof can be in a range of shorter than or equal to 600 seconds, and can be preferably in a range of shorter than or equal to 20 seconds.

The type of the reactant gas and the carrier gas included in the treatment gas, a flow rate of the reactant gas and the carrier gas at the time of forming a thin film, and the internal pressure of the chamber 10 are not particularly limited, and for example, can be in the same range as that of the first embodiment.

Third Embodiment of Method of Forming Thin Film

The methods of forming a thin film according to the first embodiment and the second embodiment may be combined with each other. In a third embodiment of the method of forming a thin film according to this embodiment, suppressing the abnormal electrical discharge by gradually decreasing the concentration of the reactant component in the first embodiment to the second concentration and suppressing the abnormal electrical discharge by gradually increasing the power level of the high-frequency power in the second embodiment to the second power level are combined. More specifically, in the plasma contact step, when the reactant component in the treatment gas is subjected to the plasma generation by applying the high-frequency power into the chamber, the first plasma generation condition in which the high-frequency power of the first power level is applied or the high-frequency power is not applied while the treatment gas in which the concentration of the reactant component is the first concentration is supplied is changed to the second plasma generation condition by gradually increasing the power level of the high-frequency power to the second power level from the first power level, and by gradually decreasing the concentration of the reactant component to the second concentration from the first concentration.

In the method of forming a thin film of this embodiment, the concentration of the reactant gas to be supplied is set to the second concentration at which a thin film of high film quality can be formed from the first concentration at which stable plasma is generated, and the high-frequency power is gradually increased to the second power level at which a thin film of high film quality can be formed from the first power level at which stable plasma is generated, and thus, stable plasma is generated in the condition of the reactant gas concentration and the power level in which stable plasma is generated, and then, the condition is adjusted to the condition of the reactant gas concentration and the power level in which a thin film of high film quality can be formed, and therefore, the generation of stable plasma is maintained. For this reason, the self-bias voltage (Vdc) has a negative value, and it is possible to generate stable plasma without any abnormal electrical discharge.

In the method of forming a thin film of this embodiment, both of the concentration of the reactant component included in the treatment gas, and the power level of the high-frequency power are varied, and thus, it is possible to decrease a variation range thereof, compared to a case where the concentration of the reactant component is independently varied or a case where the power level of the high-frequency power is independently varied. For this reason, the first concentration and the second concentration of the concentration of the reactant component included in the treatment gas can be values in the same numerical range as that of the first embodiment described above, and the first power level. And the second power level of the high-frequency power (the RF forward power (Fwd)) can be values in the same numerical range as that of the second embodiment described above.

<<Method of Modification of Surface of Thin Film>>

On the other hand, a method of modifying a surface of a thin film according to this embodiment is a method of modifying a surface of a thin film including the plasma contact step of supplying the treatment gas including at least one of the reactant gas and the carrier gas into the chamber, of activating the treatment gas by generating plasma by applying the high-frequency power, of bringing the treatment gas that is activated by the plasma generation into contact with the surface of the thin film that is formed on the substrate to modify the surface of the thin film, in which the plasma contact step is a surface modification step in which a third plasma generation condition is changed to a fourth plasma generation condition by adjusting at least one of concentration of a reactant component in the treatment gas and power level of the high-frequency power, thereby modifying the surface of the thin film while suppressing abnormal electrical discharge.

In the method of modifying a surface of a thin film according to this embodiment, first, stable plasma is generated in the third plasma generation condition or in a condition close thereto, and thus, even in a case where the third plasma generation condition is changed to the fourth plasma generation condition by adjusting at least one of the concentration of the reactant component included in the treatment gas and the power level of the high-frequency power, the generation of the stable plasma is maintained, and generation of plasma from the reactant component included in the treatment gas is accelerated by adjusting the concentration of the reactant component or the power level of the high-frequency power. According to the method of this embodiment, it is possible to perform the surface modification treatment with respect to the thin film by using stable plasma of a higher concentration, and thus, it is possible to efficiently perform a desired surface modification treatment.

[Substrate and Preparation Thereof]

The substrate W on which a thin film is deposited is installed and retained on the installation stand 12 of the chamber 10. Here, a silicon substrate, a germanium substrate, and the like can be used as the substrate W, but the substrate W is not limited thereto. In addition, examples of the thin film that is deposited on the substrate W include a SiO₂ film, a SiN film, or a SiC film. In addition, a method of depositing the thin film on the substrate W is not particularly limited, but the plasma-enhanced atomic layer deposition (PEALD) process is preferable since the thin film is deposited on a surface, and then, can be directly subjected to the surface modification treatment.

The substrate W that is installed on the installation stand 12 is heated by using a heater. Here, a heating temperature of the substrate W, for example, can be in a range of 50° C. to 500° C. At this time, the treatment gas including at least one of the reactant gas and the carrier gas is supplied into the chamber 10. Here, examples of the carrier gas included in the treatment gas include at least one selected from the group consisting of helium (He) gas, argon (Ar) gas, and hydrogen (H₂) gas. In addition, the treatment gas further includes the reactant gas, in accordance with the type of surface modification that is performed with respect to the thin film, and more specifically, may further include as the reactant gas at least one selected from the group consisting of oxygen (O₂) gas, nitrous oxide (N₂O) gas, carbon dioxide (CO₂) gas, nitrogen (N₂) gas, and ammonia (NH₃) gas. At this time, the environment in the chamber 10, for example, can be in a range of greater than or equal to 50 Pa, and can be preferably in a range of greater than or equal to 300 Pa. And an upper limit thereof can be in a range of less than or equal to 1300 Pa, and can be preferably in a range of less than or equal to 1000 Pa.

[Plasma Contact Step]

Next, the surface modification of the thin film is performed as the plasma contact step (the surface modification step) in which the treatment gas is supplied into the chamber 10, and the high-frequency power (the RF forward power (Fwd)) is applied to the gas supply unit 14, and thus, the reactant component in the treatment gas is subjected to the plasma generation, and the treatment gas that is activated by the plasma generation is brought into contact with the thin film that is formed on the substrate W.

Here, When the reactant component of the treatment gas is subjected to the plasma generation by applying the high-frequency power into the chamber, the third plasma generation condition is changed to the fourth plasma generation condition by performing at least one of gradually decreasing the concentration of the reactant component and gradually increasing the power level of the high-frequency power. Accordingly, it is possible to perform the modification treatment with respect to the surface of the thin film by using stable plasma of a higher concentration, and thus, it is possible to efficiently perform a desired modification treatment with respect to the surface of the thin film.

A treatment in which gas including the carrier gas is used as the treatment gas, and the treatment gas including the activated carrier gas is brought into contact with the surface of the thin film can be performed as the modification treatment of the thin film surface. Such treatment gas is brought into contact with the thin film, and thus, the thin film is densified, and impurities are removed, and therefore, it is possible to increase film quality of the thin film surface.

In addition, a treatment in which gas that includes reactant gas including constituent elements of the thin film and the carrier gas is used as the treatment gas, and the treatment gas including the activated reactant gas is brought into contact with the thin film surface can be performed as the modification treatment of the thin film surface. Such treatment gas is brought into contact with the thin film, and thus, atoms present at the thin film surface that have not been sufficiently reacted can be further reacted, and therefore, it is possible to increase the film quality of the thin film surface. For example, in a case where the thin film is a SiO₂ film, oxygen (O₂) gas that is activated by the plasma generation is brought into contact with the thin film, and thus, silicon (Si) atoms that have not been sufficiently oxidized can be further oxidized, and therefore, it is possible to increase the film quality of the thin film surface.

In addition, a treatment in which gas that includes reactant gas not including the constituent elements of the thin film and the carrier gas is used as the treatment gas, and the treatment gas including the activated reactant gas is brought into contact with the thin film surface can also be performed as the modification treatment of the thin film surface. Such treatment gas is brought into contact with the thin film, and thus, it is possible to change the constituent elements of the thin film surface. For example, in a case where the thin film is a SiO₂ film, nitrogen (N₂) gas that is activated by the plasma generation is brought into contact with the thin film, and thus, it is possible to form a nitride layer on the thin film surface.

The same condition as the condition of the plasma contact step in the first embodiment, the second embodiment, and the third embodiment can be used as the condition of the plasma contact step in this embodiment.

More specifically, as with the first embodiment of the method of forming a thin film, when the reactant component of the treatment gas is subjected to the plasma generation by applying the high-frequency power into the chamber, in the plasma contact step, the third plasma generation condition in which high-frequency power of a fourth power level that is identical to that of the fourth plasma generation condition described below is applied while the treatment gas in which the concentration of the reactant component is a third concentration is supplied can be changed to the fourth plasma generation condition by gradually decreasing the concentration of the reactant component to a fourth concentration from the third concentration while applying the high-frequency power of the fourth power level. Here, each of the conditions of the third concentration, the fourth concentration, and the fourth power level, configuring the third plasma generation condition and the fourth plasma generation condition, can be set to the same condition as that of the first concentration, the second concentration, and the second power level in the first embodiment of the method of forming a thin film.

In addition, as with the second embodiment of the method of forming a thin film, when the reactant component in the treatment gas is subjected to the plasma generation by applying the high-frequency power into the chamber, in the plasma contact step, the third plasma generation condition in which the high-frequency power of the third power level is applied or the high-frequency power is not applied while the treatment gas in which the concentration of the reactant component is the fourth concentration that is identical to that of the fourth plasma generation condition described below is supplied can be changed to the fourth plasma generation condition by gradually increasing the power level of the high-frequency power to the fourth power level while the treatment gas of the fourth concentration is supplied. Here, each of the conditions of the third power level, the fourth power level, and the fourth concentration, configuring the third plasma generation condition and the fourth plasma generation condition, can be the same condition as that of the first power level, second power level, and the second concentration in the second embodiment of the method of forming a thin film.

In addition, as with the third embodiment of the method of forming a thin film, when the reactant component in the treatment gas is subjected to the plasma generation by applying the high-frequency power into the chamber, in the plasma contact step, the first plasma generation condition in which the high-frequency power of the first power level is applied or the high-frequency power is not applied while the treatment gas in which the concentration of the reactant component is the first concentration is supplied can be changed to the second plasma generation condition by gradually increasing the power level of the high-frequency power to the second power level from the first power level, and by gradually decreasing the concentration of the reactant component to the second concentration from the first concentration. Here, each of the conditions of the third concentration, the third power level, the fourth power level, and the fourth concentration, configuring the third plasma generation condition and the fourth plasma generation condition, can be set to the same condition as that of the first concentration, the first power level, the second power level, and the second concentration in the third embodiment of the method of forming a thin film.

<<Combination of Method of Forming Thin Film and Method of Modifying Surface of Thin Film>>

The surface modification step of the thin film described above may be combined with the deposition step of the thin film according to the first embodiment, the second embodiment, or the third embodiment.

More specifically, the method of forming a thin film may include a first plasma contact step that is the deposition step of the thin film, and a second plasma contact step that is the surface modification step of the thin film, as the plasma contact step. Among them, in the first plasma contact step, the treatment gas including the reactant gas is supplied into the chamber, the reactant component in the treatment gas is subjected to the plasma generation by applying the high-frequency power, and the activated reactant component is brought into contact with the raw material gas component that is adsorbed on the substrate W to react with the raw material gas component, and thus, a thin film is formed. In addition, in the second plasma contact step, the treatment gas including at least one of the reactant gas and the carrier gas is supplied into the chamber, the reactant component in the treatment gas is subjected to the plasma generation by applying the high-frequency power, and the treatment gas including the activated reactant component is brought into contact with the thin film that is formed on the substrate W, and thus, the thin film is subjected to a treatment.

Here, the first plasma contact step can be performed as with the plasma contact step in the first embodiment, the second embodiment, or the third embodiment of the method of forming a thin film described above. In addition, the second plasma contact step can be performed as with the plasma contact step in the embodiment of the surface modification treatment method of a thin film described above.

Note that, in the first plasma contact step, a thin film may be formed by using the treatment gas including the reactant gas and the carrier gas, in accordance with the deposition step of the thin film according to the first embodiment, the second embodiment, or the third embodiment described above, and then, the supply of the raw material gas, and as necessary, the supply of the reactant gas may be stopped, and the thin film surface may be modified by using the carrier gas as the treatment gas, in accordance with the surface modification step of the thin film described above. Accordingly, the surface modification step of the thin film can be performed by using the same film forming device, and by using the same plasma generation condition as that of the first embodiment, the second embodiment, or the third embodiment, and thus, it is possible to more efficiently deposit and modify the thin film.

EXAMPLES

Next, examples of the present invention will be described, however, the present invention is not limited to the examples and may include variations providing such variations do not depart from the gist of the invention.

Examples 1 to 6 of Present Invention

Examples 1 to 6 of the present invention are an example of the first embodiment of the method of forming a thin film. FIG. 3 is a graph showing the power level of the high-frequency power (the RF forward power (Fwd)) to be applied, and the concentration of oxygen (O₂) that is the reactant component, in Examples 1 to 6 of the present invention. The graph is a graph at the time of changing a duration for maintaining the power level after the concentration of the reactant component reaches the second concentration (an RAMP time (1second, 5 seconds, and 9 seconds)) and the first concentration (20 volume % and 5 volume %) of the reactant component. Hereinafter, the details of test conditions and results of Examples 1 to 6 of the present invention will be described.

Example 1 of Present Invention

As illustrated in FIG. 1, the film forming device 1 was used in which the installation stand 12 of a diameter of 321 mm functioning as the lower electrode, on which the substrate W was installed on the upper surface, and the gas supply unit 14 of a diameter of 347 mm functioning as the upper electrode were provided in the chamber 10. Here, the size of the air gap D between the installation stand 12 functioning as the lower electrode and the gas supply unit 14 functioning as the upper electrode was 9.0 mm.

A silicon substrate of a diameter 300 mm was installed on the installation stand 12 in the chamber 10, as the substrate W, the substrate W was heated to a temperature of 300° C. by using the heater embedded in the installation stand 12, and helium (He) gas was supplied into the chamber 10, as the carrier gas, and thus, the internal pressure was reduced to 333 Pa.

A step of supplying raw material gas consisting of bis(diethyl amino)silane (BDEAS) into the chamber 10 in which the pressure was reduced, at a flow rate of 2000 sccm for a supply time of 0.2 seconds, was performed as the raw material gas supply step, and thus, a molecular layer of the raw material gas was formed on the surface of the substrate W. After that, the purge step was performed in which the supply of the raw material gas was stopped, and the carrier gas (helium (He) gas) was supplied into the chamber 10, and thus, the excessive raw material gas component that was not adsorbed on the substrate W was discharged from the chamber 10.

Next, the treatment gas including the carrier gas described above, and the reactant gas was supplied into the chamber 10, and then, the high-frequency power was applied to the gas supply unit 14, and thus, the reactant component in the treatment gas was subjected to the plasma generation, and was supplied onto the surface of the substrate W on which the raw material gas component was adsorbed, as the plasma contact step. Here, the generation of plasma was performed by supplying the treatment gas in which the concentration of the reactant component (oxygen (O₂) gas that was the reactant gas) was 20 volume % (the first concentration) and the remnant was formed of the carrier gas described above into the chamber 10, at a flow rate of 4000 sccm, by starting the application of the high-frequency power (the RF forward power (Fwd)) of which the power level was 200 W (the second power level), and by decreasing the concentration of the reactant component to 2 volume % (the second concentration) at a rate of change of 18 volume %/second. The high-frequency power was applied for 10 seconds after the concentration of the reactant component reached the second concentration, and thus, a molecular layer formed of silicon oxide (SiO₂) was formed on the surface of the substrate W. After that, the by-product discharge step was performed in which the application of the high-frequency power was stopped, and the carrier gas (helium (He) gas) was supplied into the chamber 10, and thus, the by-product was discharged. FIG. 4 is a graph showing a variation in the power level of the high-frequency power (the RF forward power (Fwd)), the oxygen (O₂) concentration, and the flow rate of the raw material gas, in each of the steps.

A set of steps from the raw material gas supply step to the by-product discharge step were repeated 100 times, and thus, a thin film formed of silicon oxide (SiO₂) was formed.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negative value while the thin film was formed, and thus, the abnormal electrical discharge did not occur. In addition, the WERR of the obtained thin film was 1.8, and thus, it was possible to obtain a thin film of high film quality.

Example 2 of Present Invention

The generation of the plasma in the plasma contact step was performed by supplying the treatment gas in which the concentration of the reactant component (oxygen (O₂) gas that was the reactant gas) was 20 volume % (the first concentration) and the remnant was the carrier gas formed of the carrier gas described above into the chamber 10, at a flow rate of 4000 sccm, by starting the application of the high-frequency power (the RF forward power (Fwd)) of which the power level was 200 W (the second power level), and by decreasing the concentration of the reactant component to 2 volume % (the second concentration) at a rate of change of 3.6 volume %/second. The high-frequency power was applied for 5 seconds after the concentration of the reactant component reached the second concentration, and thus, a molecular layer of silicon oxide (SiO₂) was formed on the surface of the substrate W.

The set of steps from the raw material gas supply step to the by-product discharge step were repeated 100 times in the same condition as that of Example 1 of the present invention except for the plasma contact step, and thus, a thin film formed of silicon oxide (SiO₂) was formed.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negative value while the thin film was formed, and thus, the abnormal electrical discharge did not occur. In addition, the WERR of the obtained thin film was 1.8, and thus, it was possible to obtain a thin film of high film quality.

Example 3 of Present Invention

The generation of the plasma in the plasma contact step was performed by supplying the treatment gas in which the concentration of the reactant component (oxygen (O₂) gas that was the reactant gas) was 20 volume % (the first concentration) and the remnant was formed of the carrier gas described above into the chamber 10, at a flow rate of 4000 sccm, by starting the application of the high-frequency power (the RF forward power (Fwd)) of which the power level was 200 W (the second power level), and by decreasing the concentration of the reactant component to 2 volume % (the second concentration) at a rate of change of 2 volume %/second. The high-frequency power was applied for 1second after the concentration of the reactant component reached the second concentration, and thus, a molecular layer formed of silicon oxide (SiO₂) was formed on the surface of the substrate W.

The set of steps from the raw material gas supply step to the by-product discharge step were repeated 100 times in the same condition as that of Example 1 of the present invention except for the plasma contact step, and thus, a thin film formed of silicon oxide (SiO₂) was formed.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negative value while the thin film was formed, and thus, the abnormal electrical discharge did not occur. In addition, the WERR of the obtained thin film was 1.9, and thus, it was possible to obtain a thin film of high film quality.

Example 4 of Present Invention

The generation of the plasma in the plasma contact step was performed by supplying the treatment gas in which the concentration of the reactant component (oxygen (O₂) gas that was the reactant gas) was 5 volume % (the first concentration) and the remnant was formed of the carrier gas described above into the chamber 10, at a flow rate of 4000 sccm, by starting the application of the high-frequency power (the RF forward power (Fwd)) of which the power level was 200 W (the second power level), and by decreasing the concentration of the reactant component to 2 volume % (the second concentration) at a rate of change of 3 volume %/second. The high-frequency power was applied for 9 seconds after the concentration of the reactant component reached the second concentration, and thus, a molecular layer formed of silicon oxide (SiO₂) was formed on the surface of the substrate W.

The set of steps from the raw material gas supply step to the by-product discharge step were repeated 100 times in the same condition as that of Example 1 of the present invention except for the plasma contact step, and thus, a thin film formed of silicon oxide (SiO₂) was formed.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negative value while the thin film was formed, and thus, the abnormal electrical discharge did not occur. In addition, the WERR of the obtained thin film was 1.6, and thus, it was possible to obtain a thin film of high film quality.

Example 5 of Present Invention

The generation of the plasma in the plasma contact step was performed by supplying the treatment gas in which the concentration of the reactant component (oxygen (O₂) gas that was the reactant gas) was 5 volume % (the first concentration) and the remnant was formed of the carrier gas described above into the chamber 10, at a flow rate of 4000 sccm, by starting the application of the high-frequency power (the RF forward power (Fwd)) of which the power level was 200 W (the second power level), and by decreasing the concentration of the reactant component to 2 volume % (the second concentration) at a rate of change of 0.6 volume %/second. The high-frequency power was applied for 5 seconds after the concentration of the reactant component reached the second concentration, and thus, a molecular layer formed of silicon oxide (SiO₂) was formed on the surface of the substrate W.

The set of steps from the raw material gas supply step to the by-product discharge step were repeated 100 times in the same condition as that of Example 1 of the present invention except for the plasma contact step, and thus, a thin film formed of silicon oxide (SiO₂) was formed.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negative value while the thin film was formed, and thus, the abnormal electrical discharge did not occur. In addition, the WERR of the obtained thin film was 1.7, and thus, it was possible to obtain a thin film of high film quality.

Example 6 of Present Invention

The generation of the plasma in the plasma contact step was performed by supplying the treatment gas in which the concentration of the reactant component (oxygen (O₂) gas that was the reactant gas) was 5 volume % (the first concentration) and the remnant was formed of the carrier gas described above into the chamber 10, at a flow rate of 4000 sccm, by starting the application of the high-frequency power (the RF forward power (Fwd)) of which the power level was 200 W (the second power level), and by decreasing the concentration of the reactant component to 2 volume % (the second concentration) at a rate of change of 0.33 volume %/second. The high-frequency power was applied for 1second after the concentration of the reactant component reached the second concentration, and thus, a molecular layer formed of silicon oxide (SiO₂) was formed on the surface of the substrate W.

The set of steps from the raw material gas supply step to the by-product discharge step were repeated 100 times in the same condition as that of Example 1 of the present invention except for the plasma contact step, and thus, a thin film formed of silicon oxide (SiO₂) was formed.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negative value while the thin film was formed, and thus, the abnormal electrical discharge did not occur. In addition, the WERR of the obtained thin film was 1.9, and thus, it was possible to obtain a thin film of high film quality.

Examples 7 to 12 of Present Invention

Examples 7 to 12 of the present invention are an example of the second embodiment of the method of forming a thin film. FIG. 6 is a graph showing the power level of the high-frequency power (the RF forward power (Fwd)) to be applied, and the concentration of oxygen (O₂) that is the reactant component, in Examples 7 to 12 of the present invention. The graph is a graph at the time of changing a duration for maintaining the power level after the power level reached the second power level (the RAMP time (1second, 5 seconds, and 9 seconds)) and the first power level (0 W and 150 W). Hereinafter, the details of test conditions and results of Examples 7 to 12 of the present invention will be described.

Example 7 of Present Invention

The generation of the plasma in the plasma contact step was performed by supplying the treatment gas in which the concentration of the reactant component (oxygen (O₂) gas that was the reactant gas) was 2 volume % (the second concentration) and the remnant was formed of the carrier gas described above into the chamber 10, at a flow rate of 4000 sccm, by starting the application of the high-frequency power (the RF forward power (Fwd)) of which the power level was 150 W (the first power level), and by increasing the power level to 200 W (the second power level) at a rate of change of 50 W/second. The high-frequency power was applied for 9 seconds after the power level of the high-frequency power reached the second power level, and thus, a molecular layer formed of silicon oxide (SiO₂) was formed on the surface of the substrate W.

The set of steps from the raw material gas supply step to the by-product discharge step were repeated 100 times in the same condition as that of Example 1 of the present invention except for the plasma contact step, and thus, a thin film formed of silicon oxide (SiO₂) was formed. FIG. 7 is a graph showing a variation in the power level of the high-frequency power (the RF forward power (Fwd)), the oxygen (O₂) concentration, and the flow rate of the raw material gas, in each of the steps of Example 7 of the present invention.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negative value while the thin film was formed, and thus, the abnormal electrical discharge did not occur. In addition, the WERR of the obtained thin film was 1.6, and thus, it was possible to obtain a thin film of high film quality.

Example 8 of Present Invention

The generation of the plasma in the plasma contact step was performed by supplying the treatment gas in which the concentration of the reactant component (oxygen (O₂) gas that was the reactant gas) was 2 volume % (the second concentration) and the remnant was formed of the carrier gas described above into the chamber 10, at a flow rate of 4000 sccm, by starting the application of the high-frequency power (the RF forward power (Fwd)) of which the power level was 150 W (the first power level), and by increasing the power level to 200 W (the second power level) at a rate of change of 10 W/second. The high-frequency power was applied for 5 seconds after the power level of the high-frequency power reached the second power level, and thus, a molecular layer formed of silicon oxide (SiO₂) was formed on the surface of the substrate W.

The set of steps from the raw material gas supply step to the by-product discharge step were repeated 100 times in the same condition as that of Example 1 of the present invention except for the plasma contact step, and thus, a thin film formed of silicon oxide (SiO₂) was formed.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negative value while the thin film was formed, and thus, the abnormal electrical discharge did not occur. In addition, the WERR of the obtained thin film was 1.7, and thus, it was possible to obtain a thin film of high film quality.

Example 9 of Present Invention

The generation of the plasma in the plasma contact step was performed by supplying the treatment gas in which the concentration of the reactant component (oxygen (O₂) gas that was the reactant gas) was 2 volume % (the second concentration) and the remnant was formed of the carrier gas described above into the chamber 10, at a flow rate of 4000 sccm, by starting the application of the high-frequency power (the RF forward power (Fwd)) of which the power level was 150 W (the first power level), and by increasing the power level to 200 W (the second power level) at a rate of change of 5.5 W/second. The high-frequency power was applied for 1second after the power level of the high-frequency power reached the second power level, and thus, a molecular layer formed of silicon oxide (SiO₂) was formed on the surface of the substrate W.

The set of steps from the raw material gas supply step to the by-product discharge step were repeated 100 times in the same condition as that of Example 1 of the present invention except for the plasma contact step, and thus, a thin film formed of silicon oxide (SiO₂) was formed.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negative value while the thin film was formed, and thus, the abnormal electrical discharge did not occur. In addition, the WERR of the obtained thin film was 1.8, and thus, it was possible to obtain a thin film of high film quality.

Example 10 of Present Invention

The generation of the plasma in the plasma contact step was performed by supplying the treatment gas in which the concentration of the reactant component (oxygen (O₂) gas that was the reactant gas) was 2 volume % (the second concentration) and the remnant was formed of the carrier gas described above into the chamber 10, at a flow rate of 4000 sccm, and by increasing the power level to 200 W (the second power level) from a state in which the high-frequency power (the RF forward power (Fwd)) was not applied (a state in which the first power level was 0 W), at a rate of change of 200 W/second. The high-frequency power of the second power level was applied for 9 seconds after the power level of the high-frequency power reached the second power level, and thus, a molecular layer formed of silicon oxide (SiO₂) was formed on the surface of the substrate W.

The set of steps from the raw material gas supply step to the by-product discharge step were repeated 100 times in the same condition as that of Example 1 of the present invention except for the plasma contact step, and thus, a thin film formed of silicon oxide (SiO₂) was formed.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negative value while the thin film was formed, and thus, the abnormal electrical discharge did not occur. In addition, the WERR of the obtained thin film was 1.7, and thus, it was possible to obtain a thin film of high film quality.

Example 11 of Present Invention

The generation of the plasma in the plasma contact step was performed by supplying the treatment gas in which the concentration of the reactant component (oxygen (O₂) gas that was the reactant gas) was 2 volume % (the second concentration) and the remnant was formed of the carrier gas described above into the chamber 10, at a flow rate of 4000 sccm, and by increasing the power level to 200 W (the second power level) from a state in which the high-frequency power (the RF forward power (Fwd)) was not applied (a state in which the first power level was 0 W), at a rate of change of 40 W/second. The high-frequency power of the second power level was applied for 5 seconds after the power level of the high-frequency power reached the second power level, and thus, a molecular layer formed of silicon oxide (SiO₂) was formed on the surface of the substrate W.

The set of steps from the raw material gas supply step to the by-product discharge step were repeated four times in the same condition as that of Example 1 of the present invention except for the plasma contact step, and thus, a thin film formed of silicon oxide (SiO₂) was formed.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negative value while the thin film was formed, and thus, the abnormal electrical discharge did not occur. In addition, the WERR of the obtained thin film was 1.8, and thus, it was possible to obtain a thin film of high film quality.

Example 12 of Present Invention

The generation of the plasma in the plasma contact step was performed by supplying the treatment gas in which the concentration of the reactant component (oxygen (O₂) gas that was the reactant gas) was 2 volume % (the second concentration) and the remnant was formed of the carrier gas described above into the chamber 10, at a flow rate of 4000 sccm, and by increasing the power level to 200 W (the second power level) from a state in which the high-frequency power (the RF forward power (Fwd)) was not applied (a state in which the first power level was 0 W), at a rate of change of 22 W/second. The high-frequency power of the second power level was applied for 1second after the power level of the high-frequency power reached the second power level, and thus, a molecular layer formed of silicon oxide (SiO₂) was formed on the surface of the substrate W.

The set of steps from the raw material gas supply step to the by-product discharge step were repeated 100 times in the same condition as that of Example 1 of the present invention except for the plasma contact step, and thus, a thin film formed of silicon oxide (SiO₂) was formed.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negative value while the thin film was formed, and thus, the abnormal electrical discharge did not occur. In addition, the WERR of the obtained thin film was 1.9, and thus, it was possible to obtain a thin film of high film quality.

Examples 13 to 16 of Present Invention

Examples 13 to 16 of the present invention are an example of the method of forming a thin film according to the third embodiment. FIG. 8 is a graph showing the power level of the high-frequency power (the RF forward power (Fwd)) to be applied and the concentration of oxygen (O₂) that is the reactant component, in Examples 13 to 16 of the present invention. The graph is a graph at the time of changing the first concentration (5% and 10%) of the reactant component, and the first power level (50 W and 150 W). Hereinafter, the details of test conditions and results of Examples 13 to 16 of the present invention will be described.

Example 13 of Present Invention

The generation of the plasma in the plasma contact step was performed by supplying the treatment gas in which the concentration of the reactant component (oxygen (O₂) gas that was the reactant gas) was 5 volume % (the first concentration) and the remnant was formed of the carrier gas described above into the chamber 10, at a flow rate of 4000 sccm, by starting the application of the high-frequency power (the RF forward power (Fwd)) of which the power level was 50 W (the first power level), and by decreasing the concentration of the reactant component to 2 volume % (the second concentration) at a rate of change of 0.6 volume %/second and by increasing the power level to 200 W (the second power level) at a rate of change of 30 W/second. The high-frequency power was applied for 5 seconds after the concentration of the reactant component reached the second concentration and the power level of the high-frequency power reached the second power level, and thus, a molecular layer formed of silicon oxide (SiO₂) was formed on the surface of the substrate W.

The set of steps from the raw material gas supply step to the by-product discharge step were repeated 100 times in the same condition as that of Example 1 of the present invention except for the plasma contact step, and thus, a thin film of silicon oxide (SiO₂) was formed.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negative value while the thin film was formed, and thus, the abnormal electrical discharge did not occur. In addition, the WERR of the obtained thin film was 1.8, and thus, it was possible to obtain a thin film of high film quality.

Example 14 of Present Invention

The generation of the plasma in the plasma contact step was performed by supplying the treatment gas in which the concentration of the reactant component (oxygen (O₂) gas that was the reactant gas) was 10 volume % (the first concentration) and the remnant was formed of the carrier gas described above into the chamber 10, at a flow rate of 4000 sccm, by starting the application of the high-frequency power (the RF forward power (Fwd)) of which the power level was 50 W (the first power level), and by decreasing the concentration of the reactant component to 2 volume % (the second concentration) at a rate of change of 1.6 volume %/second and by increasing the power level to 200 W (the second power level) at a rate of change of 30 W/second. The high-frequency power was applied for 5 seconds after the concentration of the reactant component reached the second concentration and the power level of the high-frequency power reached the second power level, and thus, a molecular layer formed of silicon oxide (SiO₂) was formed on the surface of the substrate W.

The set of steps from the raw material gas supply step to the by-product discharge step were repeated 100 times in the same condition as that of Example 1 of the present invention except for the plasma contact step, and thus, a thin film formed of silicon oxide (SiO₂) was formed.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negative value while the thin film was formed, and thus, the abnormal electrical discharge did not occur. In addition, the WERR of the obtained thin film was 1.9, and thus, it was possible to obtain a thin film of high film quality.

Example 15 of Present Invention

The generation of the plasma in the plasma contact step was performed by supplying the treatment gas in which the concentration of the reactant component (oxygen (O₂) gas that was the reactant gas) was 5 volume % (the first concentration) and the remnant was formed of the carrier gas described above into the chamber 10, at a flow rate of 4000 sccm, by starting the application of the high-frequency power (the RF forward power (Fwd)) of which the power level was 150 W (the first power level), and by decreasing the concentration of the reactant component to 2 volume % (the second concentration) at a rate of change of 0.6 volume %/second and by increasing the power level to 200 W (the second power level) at a rate of change of 10 W/second. The high-frequency power was applied for 5 seconds after the concentration of the reactant component reached the second concentration and the power level of the high-frequency power reached the second power level, and thus, a molecular layer formed of silicon oxide (SiO₂) was formed on the surface of the substrate W.

The set of steps from the raw material gas supply step to the by-product discharge step were repeated 100 times in the same condition as that of Example 1 of the present invention except for the plasma contact step, and thus, a thin film formed of silicon oxide (SiO₂) was formed.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negative value while the thin film was formed, and thus, the abnormal electrical discharge did not occur. In addition, the WERR of the obtained thin film was 1.6, and thus, it was possible to obtain a thin film of high film quality.

Example 16 of Present Invention

The generation of the plasma in the plasma contact step was performed by supplying the treatment gas in which the concentration of the reactant component (oxygen (O₂) gas that was the reactant gas) was 10 volume % (the first concentration) and the remnant was formed of the carrier gas described above into the chamber 10, at a flow rate of 4000 sccm, by starting the application of the high-frequency power (the RF forward power (Fwd)) of which the power level was 150 W (the first power level), and by decreasing the concentration of the reactant component to 2 volume % (the second concentration) at a rate of change of 1.6 volume %/second and by increasing the power level to 200 W (the second power level) at a rate of change of 10 W/second. The high-frequency power was applied for 5 seconds after the concentration of the reactant component reached the second concentration and the power level of the high-frequency power reached the second power level, and thus, a molecular layer formed of silicon oxide (SiO₂) was formed on the surface of the substrate W.

The set of steps from the raw material gas supply step to the by-product discharge step were repeated 100 times in the same condition as that of Example 1 of the present invention except for the plasma contact step, and thus, a thin film formed of silicon oxide (SiO₂) was formed.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negative value while the thin film was formed, and thus, the abnormal electrical discharge did not occur. In addition, the WERR of the obtained thin film was 1.7, and thus, it was possible to obtain a thin film of high film quality.

Comparative Example 1

The generation of the plasma in the plasma contact step was performed by supplying the treatment gas in which the concentration of the reactant component (oxygen (O₂) gas that was the reactant gas) was 2 volume % and the remnant was formed of the carrier gas described above into the chamber 10, at a flow rate of 4000 sccm, and by starting the application of the high-frequency power (the RF forward power (Fwd)) of which the power level was 200 W, without varying the concentration of the reactant component and the power level of the high-frequency power. The high-frequency power was applied for 10 seconds after the application of the high-frequency power was started, and thus, a molecular layer formed of silicon oxide (SiO₂) was formed on the surface of the substrate W.

The set of steps from the raw material gas supply step to the by-product discharge step were repeated 100 times in the same condition as that of Example 1 of the present invention except for the plasma contact step, and thus, a thin film formed of silicon oxide (SiO₂) was formed. FIG. 9 is a graph showing a variation in the power level of the high-frequency power (the RF forward power (Fwd)), the oxygen (O₂) concentration, and the flow rate of the raw material gas, in each of the steps.

As a result thereof, as shown in FIG. 12, the self-bias voltage (Vdc) had a positive value around 5 V while the high-frequency power was applied, and thus, the abnormal electrical discharge occurred. In addition, the WERR of the obtained thin film was 2.0, and thus, the film quality was low.

Examples 17 and 18 of Present Invention

Examples 17 and 18 of the present invention are an example of a method of forming a thin film according to a fourth embodiment. Hereinafter, the details of test conditions and results of Examples 17 and 18 of the present invention will be described.

Example 17 of Present Invention

A thin film formed of silicon oxide (SiO₂) was deposited on the silicon substrate by using the same film forming device 1 as that of Example 1 of the present invention, in accordance with the same method as that of Comparative Example 1, and then, the supply of oxygen (O₂) gas that was the reactant gas was stopped, and only the supply of helium (He) gas that was the carrier gas was performed, and thus, the internal pressure was reduced to 333 Pa.

The carrier gas was subjected to the plasma generation by applying the high-frequency power to the gas supply unit 14 while the treatment gas formed of the carrier gas that was the reactant component was supplied into the chamber 10 in which the pressure was reduced, and was supplied onto the surface of the substrate W on which the raw material gas component was adsorbed, as the plasma contact step. Here, the generation of plasma was performed by supplying the carrier gas into the chamber 10 at a flow rate of 4000 sccm, by starting the application of the high-frequency power (the RF forward power (Fwd)) of which the power level was 150 W (the first power level), and by increasing the power level to 200 W (the second power level) at a rate of change of 50 W/second. The high-frequency power was applied for 9 seconds after the power level of the high-frequency power reached the second power level, and thus, the thin film formed of silicon oxide (SiO₂) that was deposited on the surface of the substrate W was densified, and the impurities were removed, and therefore, a treatment of increasing the film quality was performed. FIG. 10 is a graph showing a variation in the power level of the high-frequency power (the RF forward power (Fwd)), the oxygen (O₂) concentration, and the flow rate of the raw material gas, in each of the steps.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negative value while the thin film was formed, and thus, the abnormal electrical discharge did not occur. In addition, the WERR of the thin film after the treatment was 1.7, and thus, it was possible to obtain a thin film of desired high film quality.

Example 18 of Present Invention

A thin film formed of silicon oxide (SiO₂) was deposited on the silicon substrate by using the same film forming device 1 as that of Example 1 of the present invention, in accordance with the same method as that of Comparative Example 1, and then, the plasma contact step was performed by supplying the treatment gas in which the concentration of the reactant component (oxygen (O₂) gas that was the reactant gas) was 2 volume % and the remnant was formed of the carrier gas described above into the chamber 10 in which the pressure was reduced, at a flow rate of 4000 sccm, by starting the application of the high-frequency power (the RF forward power (Fwd)) of which the power level was 20 W (the second power level), and by decreasing the concentration of the reactant gas to 2 volume % (the second concentration) at a rate of change of 9 volume %/second. The high-frequency power was applied for 18 seconds after the concentration of the reactant gas reached the second concentration, and thus, silicon (Si) atoms that had not been sufficiently oxidized, included in the surface of the thin film formed of silicon oxide (SiO₂) that was deposited on the surface of the substrate W, was further oxidized, and thus, the treatment of increasing the film quality was performed. FIG. 11 is a graph showing a variation in the power level of the high-frequency power (the RF forward power (Fwd)), the oxygen (O₂) concentration, and the flow rate of the raw material gas, in each of the steps.

As a result thereof, the self-bias voltage (Vdc) had 0 or a negative value while the thin film was formed, and thus, the abnormal electrical discharge did not occur. In addition, the WERR of the thin film after the treatment was 1.9, and thus, it was possible to increase the film quality of the thin film.

Conclusion

From the results described above, it was confirmed that in the method of forming a thin film (Examples 1 to 18 of Present Invention) in which the abnormal electrical discharge is suppressed by increasing the high-frequency power to the second power level, by gradually decreasing the treatment gas to the second concentration, and/or, by gradually increasing the high-frequency power to the second power level, from the first plasma generation condition in which stable plasma was generated, it was possible to obtain a thin film of higher film quality, and to obtain a desired thin film, compared to the method of forming a thin film of Comparative Example 1.

EXPLANATION OF REFERENCE NUMERALS

1 FILM FORMING DEVICE

10 CHAMBER

11 INSERTION HOLE

12 INSTALLATION STAND

13, 16 SUPPORT MEMBER

14 GAS SUPPLY UNIT

15 GAS SUPPLY HOLE

W SUBSTRATE

D AIR GAP 

What is claimed is:
 1. A method of forming a thin film on a surface of a substrate, the method comprising: a plasma contact step including supplying a treatment gas including a reactant gas into a chamber, activating a reactant component included in the treatment gas by generating plasma from the reactant component by applying high-frequency power, and bringing the treatment gas including the reactant component thus activated into contact with the surface of the substrate to form the thin film, wherein in the plasma contact step, a first plasma generation condition is changed to a second plasma generation condition by adjusting at least one of concentration of the reactant component included in the treatment gas and power level of the high-frequency power, thereby suppressing abnormal electrical discharge.
 2. The method of claim 1, wherein in the first plasma generation condition, high-frequency power of a second power level that is identical to that of the second plasma generation condition is applied while treatment gas in which the concentration of the reactant component is a first concentration is supplied, and the concentration of the reactant component is decreased to a second concentration from the first concentration while the high-frequency power of the second power level is applied, to thereby change the first plasma generation condition to the second plasma generation condition.
 3. The method of claim 1, wherein in the first plasma generation condition, high-frequency power of a first power level is applied or the high-frequency power is not applied while treatment gas in which the concentration of the reactant component is a second concentration that is identical to that of the second plasma generation condition is supplied, and the power level of the high-frequency power is increased to a second power level while the treatment gas of the second concentration is supplied, to thereby change the first plasma generation condition to the second plasma generation condition.
 4. The method of claim 1, wherein in the first plasma generation condition, high-frequency power of a first power level is applied or the high-frequency power is not applied while treatment gas in which the concentration of the reactant component is a first concentration is supplied, and the power level of the high-frequency power is increased to a second power level from the first power level, and the concentration of the reactant component is decreased to a second concentration, to thereby change the first plasma generation condition to the second plasma generation condition.
 5. The method of claim 1, further comprising: before the plasma contact step, a supply step of supplying at least a raw material gas including a raw material gas component into the chamber and adsorbing the raw material gas component on the surface of the substrate; and a discharge step of discharging any of the raw material gas component that is not adsorbed on the surface of the substrate from the chamber, wherein the plasma contact step is a thin film deposition step performed by a plasma-enhanced atomic layer deposition (PEALD) process in which the treatment gas including the reactant gas supplied into the chamber also includes a carrier gas, the reactant component consists of at least one of the reactant gas and the carrier gas, activation of the reactant component includes generating plasma from the reactant component by applying high-frequency power, and the reactant component thus activated reacts with the raw material gas component that is adsorbed on the surface of the substrate to form the thin film.
 6. The method of claim 5, wherein the raw material gas is aminosilane.
 7. The method of claim 5, wherein the reactant gas is at least one selected from the group consisting of oxygen (O₂) gas, nitrous oxide (N₂O) gas, carbon dioxide (CO₂) gas, nitrogen (N₂) gas, and ammonia (NH₃) gas.
 8. The method of claim 5, wherein the carrier gas is at least one selected from the group consisting of helium (He) gas, argon (Ar) gas, and hydrogen (H₂) gas.
 9. The method of claim 1, wherein the thin film consists of a SiO₂ film, a SiN film, or a SiC film.
 10. A method of modifying a surface of a thin film formed on a substrate, the method comprising: a plasma contact step including supplying treatment gas including at least one of a reactant gas and carrier gas into a chamber, activating the treatment gas by generating plasma by applying high-frequency power to the treatment gas, and bringing the treatment gas thus activated by the generation of plasma into contact with the surface of the thin film formed on the substrate to modify the surface of the thin film, wherein the plasma contact step is a surface modification step in which a third plasma generation condition is changed to a fourth plasma generation condition by adjusting at least one of concentration of a reactant component included in the treatment gas and power level of the high-frequency power, thereby suppressing abnormal electrical discharge. 